The invention relates to an arrangement for treating a fiber web. Particularly, but not solely, the invention relates to an arrangement for sizing paper and board web, in particular for sizing paper and board web. Especially the invention relates to an arrangement for treating a fiber web, where a sizer has sizing equipment located on both sides of the web and size press rolls located on both sides of the web and between which a size nip is formed.
The sizing of paper and board web typically utilizes a separate sizer. In connection with the sizer different kinds of sizing technology are employed in prior art arrangements, for example pond sizing technology or film transfer technology or spray sizing technology. WO publication 03/004770 A1 discloses a further method for manufacturing a surface sized web of paper of paperboard, the method comprising a step of applying to at least one side of the web an aqueous furnish of size and according to the method the solids content of the size furnish being applied is at least 15% and the size furnish is applied to one side of the web by an amount not greater than 5 g/m2 as aqueous furnish of size applied to the web. As one suitable, among others, applicator apparatus for the method disclosed, the publication mentions spray applicators. Further, WO publication 2006/058961 A1 discloses a method and arrangement for processing a paper or board web or similar fiber web. In this prior art method a processing mixture is spread on the surface of the web with spray nozzles. In the method the web to be processed is lead from a press nip and between rolls in this nip. Before the web enters the nip such an amount of processing mixture is spread onto at least one side of the web so that the processing mixture is still wet when it enters the nip. In the prior art arrangement according to this publication the arrangement comprises at least one press nip, elements for taking the web to the press nip, and elements for spreading the processing mixture, wherein the elements for spreading the processing mixture are spray nozzles which are arranged at an adjustable distance in the arrival direction of the web from the press nip to feed the processing mixture to at least one surface of the web.
A typical web transfer route according to the prior art in connection with spray sizing apparatuses is shown schematically in FIG. 1. The fiber web W is guided by guide rolls 1, 2 to the sizer 10, comprising spray sizing equipments 3, 4 and size press rolls 5, 6 forming a size nip and which rolls 5, 6 are located on both sides of the web W. After the spray sizing equipments 3, 4 the web W is guided into the size nip i.e. size press of the sizer 10, which sizer press comprises two size press rolls 5, 6 between which the size nip is formed. In the production line the fiber web W is produced such that the front side of the finished web W is the side shown in the figure as top side TS of the web W and in the figure the bottom side BS of the web W will be the back side of the finished web product. By front side of the finished product is meant the side that, for example in a final product made of the fiber web such as a cardboard box, is on the outside and thus in the view of the customer. Thus it is required of the fiber web production that the side of the web that will be the front side of the finished web product must be free from defects and of prefect quality, but, on the other hand, the side of the web that will be the back side of the finished web product may contain defects as it is not in view on the product. One problem in prior art web transfer in connection with the sizer 10 comprising spray sizing apparatuses is that sometimes the spray sizing equipment 4 located above the web i.e. on the top size of the web W might drop size droplets on the top of the web thus creating a defect to the front side of the final product.
CN utility model 201099804 discloses a mica paper gluing machine, which comprises a roller guide apparatus arranged at the back of a mica paper roll. A guide roll is used in the machine to change the transfer direction of the web.
A film coater is disclosed in US patent application publication 2008/0087216 in which one or more coaters are utilized to transfer coating to the outer surfaces of at least one more rolls, which in turn transfer the coating from the roll surfaces to one or more sides of the web for coating paper. The web runs upwardly past a guide roll and into and through the nip where the film of coating is applied to the outer surface of each roll by a corresponding coating applicator and is transferred to a corresponding side of the web. While film split action may occur, the resulting film droplets fall back onto the roll surfaces and not onto the web as would result if the web would run downwardly.
This has been tried to be solved in the prior art by arranging the web transfer route to be vertical via the spray equipment, but this vertical transfer is problematic in some cases because an air drying device remains between sizer frames.